/*

This is an implementation of the AES128 algorithm, specifically ECB and CBC mode.

The implementation is verified against the test vectors in:
  National Institute of Standards and Technology Special Publication 800-38A 2001 ED

ECB-AES128
----------

  plain-text:
    6bc1bee22e409f96e93d7e117393172a
    ae2d8a571e03ac9c9eb76fac45af8e51
    30c81c46a35ce411e5fbc1191a0a52ef
    f69f2445df4f9b17ad2b417be66c3710

  key:
    2b7e151628aed2a6abf7158809cf4f3c

  resulting cipher
    3ad77bb40d7a3660a89ecaf32466ef97
    f5d3d58503b9699de785895a96fdbaaf
    43b1cd7f598ece23881b00e3ed030688
    7b0c785e27e8ad3f8223207104725dd4


NOTE:   String length must be evenly divisible by 16byte (str_len % 16 == 0)
        You should pad the end of the string with zeros if this is not the case.

*/

/*****************************************************************************/
/* Includes:                                                                 */
/*****************************************************************************/
#include <stdint.h>
#include <string.h>  // CBC mode, for memset
#include "aes.h"

/*****************************************************************************/
/* Defines:                                                                  */
/*****************************************************************************/
// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4
// The number of 32 bit words in a key.
#define Nk 4
// Key length in bytes [128 bit]
#define KEYLEN 16
// The number of rounds in AES Cipher.
#define Nr 10

// jcallan@github points out that declaring Multiply as a function
// reduces code size considerably with the Keil ARM compiler.
// See this link for more information: https://github.com/kokke/tiny-AES128-C/pull/3
#ifndef MULTIPLY_AS_A_FUNCTION
#define MULTIPLY_AS_A_FUNCTION 0
#endif

/*****************************************************************************/
/* Private variables:                                                        */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
typedef uint8_t state_t[4][4];
static state_t *state;

// The array that stores the round keys.
static uint8_t RoundKey[176];

// The Key input to the AES Program
static const uint8_t *Key;

#if defined(CBC) && CBC
// Initial Vector used only for CBC mode
static uint8_t *Iv;
#endif

// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM -
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static const uint8_t sbox[256] = {
    //0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
    0x63,
    0x7c,
    0x77,
    0x7b,
    0xf2,
    0x6b,
    0x6f,
    0xc5,
    0x30,
    0x01,
    0x67,
    0x2b,
    0xfe,
    0xd7,
    0xab,
    0x76,
    0xca,
    0x82,
    0xc9,
    0x7d,
    0xfa,
    0x59,
    0x47,
    0xf0,
    0xad,
    0xd4,
    0xa2,
    0xaf,
    0x9c,
    0xa4,
    0x72,
    0xc0,
    0xb7,
    0xfd,
    0x93,
    0x26,
    0x36,
    0x3f,
    0xf7,
    0xcc,
    0x34,
    0xa5,
    0xe5,
    0xf1,
    0x71,
    0xd8,
    0x31,
    0x15,
    0x04,
    0xc7,
    0x23,
    0xc3,
    0x18,
    0x96,
    0x05,
    0x9a,
    0x07,
    0x12,
    0x80,
    0xe2,
    0xeb,
    0x27,
    0xb2,
    0x75,
    0x09,
    0x83,
    0x2c,
    0x1a,
    0x1b,
    0x6e,
    0x5a,
    0xa0,
    0x52,
    0x3b,
    0xd6,
    0xb3,
    0x29,
    0xe3,
    0x2f,
    0x84,
    0x53,
    0xd1,
    0x00,
    0xed,
    0x20,
    0xfc,
    0xb1,
    0x5b,
    0x6a,
    0xcb,
    0xbe,
    0x39,
    0x4a,
    0x4c,
    0x58,
    0xcf,
    0xd0,
    0xef,
    0xaa,
    0xfb,
    0x43,
    0x4d,
    0x33,
    0x85,
    0x45,
    0xf9,
    0x02,
    0x7f,
    0x50,
    0x3c,
    0x9f,
    0xa8,
    0x51,
    0xa3,
    0x40,
    0x8f,
    0x92,
    0x9d,
    0x38,
    0xf5,
    0xbc,
    0xb6,
    0xda,
    0x21,
    0x10,
    0xff,
    0xf3,
    0xd2,
    0xcd,
    0x0c,
    0x13,
    0xec,
    0x5f,
    0x97,
    0x44,
    0x17,
    0xc4,
    0xa7,
    0x7e,
    0x3d,
    0x64,
    0x5d,
    0x19,
    0x73,
    0x60,
    0x81,
    0x4f,
    0xdc,
    0x22,
    0x2a,
    0x90,
    0x88,
    0x46,
    0xee,
    0xb8,
    0x14,
    0xde,
    0x5e,
    0x0b,
    0xdb,
    0xe0,
    0x32,
    0x3a,
    0x0a,
    0x49,
    0x06,
    0x24,
    0x5c,
    0xc2,
    0xd3,
    0xac,
    0x62,
    0x91,
    0x95,
    0xe4,
    0x79,
    0xe7,
    0xc8,
    0x37,
    0x6d,
    0x8d,
    0xd5,
    0x4e,
    0xa9,
    0x6c,
    0x56,
    0xf4,
    0xea,
    0x65,
    0x7a,
    0xae,
    0x08,
    0xba,
    0x78,
    0x25,
    0x2e,
    0x1c,
    0xa6,
    0xb4,
    0xc6,
    0xe8,
    0xdd,
    0x74,
    0x1f,
    0x4b,
    0xbd,
    0x8b,
    0x8a,
    0x70,
    0x3e,
    0xb5,
    0x66,
    0x48,
    0x03,
    0xf6,
    0x0e,
    0x61,
    0x35,
    0x57,
    0xb9,
    0x86,
    0xc1,
    0x1d,
    0x9e,
    0xe1,
    0xf8,
    0x98,
    0x11,
    0x69,
    0xd9,
    0x8e,
    0x94,
    0x9b,
    0x1e,
    0x87,
    0xe9,
    0xce,
    0x55,
    0x28,
    0xdf,
    0x8c,
    0xa1,
    0x89,
    0x0d,
    0xbf,
    0xe6,
    0x42,
    0x68,
    0x41,
    0x99,
    0x2d,
    0x0f,
    0xb0,
    0x54,
    0xbb,
    0x16};

static const uint8_t rsbox[256] =
    {0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d};

// The round constant word array, Rcon[i], contains the values given by
// x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
// Note that i starts at 1, not 0).
static const uint8_t Rcon[255] = {
    0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb};

/*****************************************************************************/
/* Private functions:                                                        */
/*****************************************************************************/
static uint8_t getSBoxValue(uint8_t num)
{
    return sbox[num];
}

static uint8_t getSBoxInvert(uint8_t num)
{
    return rsbox[num];
}

// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
static void KeyExpansion(void)
{
    uint32_t i, j, k;
    uint8_t  tempa[4];  // Used for the column/row operations

    // The first round key is the key itself.
    for (i = 0; i < Nk; ++i)
    {
        RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
        RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
        RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
        RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
    }

    // All other round keys are found from the previous round keys.
    for (; (i < (Nb * (Nr + 1))); ++i)
    {
        for (j = 0; j < 4; ++j)
        {
            tempa[j] = RoundKey[(i - 1) * 4 + j];
        }
        if (i % Nk == 0)
        {
            // This function rotates the 4 bytes in a word to the left once.
            // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

            // Function RotWord()
            {
                k        = tempa[0];
                tempa[0] = tempa[1];
                tempa[1] = tempa[2];
                tempa[2] = tempa[3];
                tempa[3] = k;
            }

            // SubWord() is a function that takes a four-byte input word and
            // applies the S-box to each of the four bytes to produce an output word.

            // Function Subword()
            {
                tempa[0] = getSBoxValue(tempa[0]);
                tempa[1] = getSBoxValue(tempa[1]);
                tempa[2] = getSBoxValue(tempa[2]);
                tempa[3] = getSBoxValue(tempa[3]);
            }

            tempa[0] = tempa[0] ^ Rcon[i / Nk];
        }
        else if (Nk > 6 && i % Nk == 4)
        {
            // Function Subword()
            {
                tempa[0] = getSBoxValue(tempa[0]);
                tempa[1] = getSBoxValue(tempa[1]);
                tempa[2] = getSBoxValue(tempa[2]);
                tempa[3] = getSBoxValue(tempa[3]);
            }
        }
        RoundKey[i * 4 + 0] = RoundKey[(i - Nk) * 4 + 0] ^ tempa[0];
        RoundKey[i * 4 + 1] = RoundKey[(i - Nk) * 4 + 1] ^ tempa[1];
        RoundKey[i * 4 + 2] = RoundKey[(i - Nk) * 4 + 2] ^ tempa[2];
        RoundKey[i * 4 + 3] = RoundKey[(i - Nk) * 4 + 3] ^ tempa[3];
    }
}

// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static void AddRoundKey(uint8_t round)
{
    uint8_t i, j;
    for (i = 0; i < 4; ++i)
    {
        for (j = 0; j < 4; ++j)
        {
            (*state)[i][j] ^= RoundKey[round * Nb * 4 + i * Nb + j];
        }
    }
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void SubBytes(void)
{
    uint8_t i, j;
    for (i = 0; i < 4; ++i)
    {
        for (j = 0; j < 4; ++j)
        {
            (*state)[j][i] = getSBoxValue((*state)[j][i]);
        }
    }
}

// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static void ShiftRows(void)
{
    uint8_t temp;

    // Rotate first row 1 columns to left
    temp           = (*state)[0][1];
    (*state)[0][1] = (*state)[1][1];
    (*state)[1][1] = (*state)[2][1];
    (*state)[2][1] = (*state)[3][1];
    (*state)[3][1] = temp;

    // Rotate second row 2 columns to left
    temp           = (*state)[0][2];
    (*state)[0][2] = (*state)[2][2];
    (*state)[2][2] = temp;

    temp           = (*state)[1][2];
    (*state)[1][2] = (*state)[3][2];
    (*state)[3][2] = temp;

    // Rotate third row 3 columns to left
    temp           = (*state)[0][3];
    (*state)[0][3] = (*state)[3][3];
    (*state)[3][3] = (*state)[2][3];
    (*state)[2][3] = (*state)[1][3];
    (*state)[1][3] = temp;
}

static uint8_t xtime(uint8_t x)
{
    return ((x << 1) ^ (((x >> 7) & 1) * 0x1b));
}

// MixColumns function mixes the columns of the state matrix
static void MixColumns(void)
{
    uint8_t i;
    uint8_t Tmp, Tm, t;
    for (i = 0; i < 4; ++i)
    {
        t   = (*state)[i][0];
        Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3];
        Tm  = (*state)[i][0] ^ (*state)[i][1];
        Tm  = xtime(Tm);
        (*state)[i][0] ^= Tm ^ Tmp;
        Tm = (*state)[i][1] ^ (*state)[i][2];
        Tm = xtime(Tm);
        (*state)[i][1] ^= Tm ^ Tmp;
        Tm = (*state)[i][2] ^ (*state)[i][3];
        Tm = xtime(Tm);
        (*state)[i][2] ^= Tm ^ Tmp;
        Tm = (*state)[i][3] ^ t;
        Tm = xtime(Tm);
        (*state)[i][3] ^= Tm ^ Tmp;
    }
}

// Multiply is used to multiply numbers in the field GF(2^8)
#if MULTIPLY_AS_A_FUNCTION
static uint8_t Multiply(uint8_t x, uint8_t y)
{
    return (((y & 1) * x) ^
            ((y >> 1 & 1) * xtime(x)) ^
            ((y >> 2 & 1) * xtime(xtime(x))) ^
            ((y >> 3 & 1) * xtime(xtime(xtime(x)))) ^
            ((y >> 4 & 1) * xtime(xtime(xtime(xtime(x))))));
}
#else
#define Multiply(x, y)                         \
    (((y & 1) * x) ^                           \
     ((y >> 1 & 1) * xtime(x)) ^               \
     ((y >> 2 & 1) * xtime(xtime(x))) ^        \
     ((y >> 3 & 1) * xtime(xtime(xtime(x)))) ^ \
     ((y >> 4 & 1) * xtime(xtime(xtime(xtime(x))))))

#endif

// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
static void InvMixColumns(void)
{
    int     i;
    uint8_t a, b, c, d;
    for (i = 0; i < 4; ++i)
    {
        a = (*state)[i][0];
        b = (*state)[i][1];
        c = (*state)[i][2];
        d = (*state)[i][3];

        (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
        (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
        (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
        (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
    }
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void InvSubBytes(void)
{
    uint8_t i, j;
    for (i = 0; i < 4; ++i)
    {
        for (j = 0; j < 4; ++j)
        {
            (*state)[j][i] = getSBoxInvert((*state)[j][i]);
        }
    }
}

static void InvShiftRows(void)
{
    uint8_t temp;

    // Rotate first row 1 columns to right
    temp           = (*state)[3][1];
    (*state)[3][1] = (*state)[2][1];
    (*state)[2][1] = (*state)[1][1];
    (*state)[1][1] = (*state)[0][1];
    (*state)[0][1] = temp;

    // Rotate second row 2 columns to right
    temp           = (*state)[0][2];
    (*state)[0][2] = (*state)[2][2];
    (*state)[2][2] = temp;

    temp           = (*state)[1][2];
    (*state)[1][2] = (*state)[3][2];
    (*state)[3][2] = temp;

    // Rotate third row 3 columns to right
    temp           = (*state)[0][3];
    (*state)[0][3] = (*state)[1][3];
    (*state)[1][3] = (*state)[2][3];
    (*state)[2][3] = (*state)[3][3];
    (*state)[3][3] = temp;
}

// Cipher is the main function that encrypts the PlainText.
static void Cipher(void)
{
    uint8_t round = 0;

    // Add the First round key to the state before starting the rounds.
    AddRoundKey(0);

    // There will be Nr rounds.
    // The first Nr-1 rounds are identical.
    // These Nr-1 rounds are executed in the loop below.
    for (round = 1; round < Nr; ++round)
    {
        SubBytes();
        ShiftRows();
        MixColumns();
        AddRoundKey(round);
    }

    // The last round is given below.
    // The MixColumns function is not here in the last round.
    SubBytes();
    ShiftRows();
    AddRoundKey(Nr);
}

static void InvCipher(void)
{
    uint8_t round = 0;

    // Add the First round key to the state before starting the rounds.
    AddRoundKey(Nr);

    // There will be Nr rounds.
    // The first Nr-1 rounds are identical.
    // These Nr-1 rounds are executed in the loop below.
    for (round = Nr - 1; round > 0; round--)
    {
        InvShiftRows();
        InvSubBytes();
        AddRoundKey(round);
        InvMixColumns();
    }

    // The last round is given below.
    // The MixColumns function is not here in the last round.
    InvShiftRows();
    InvSubBytes();
    AddRoundKey(0);
}

static void BlockCopy(uint8_t *output, uint8_t *input)
{
    uint8_t i;
    for (i = 0; i < KEYLEN; ++i)
    {
        output[i] = input[i];
    }
}

/*****************************************************************************/
/* Public functions:                                                         */
/*****************************************************************************/
#if defined(ECB) && ECB

void AES128_ECB_encrypt(uint8_t *input, const uint8_t *key, uint8_t *output)
{
    // Copy input to output, and work in-memory on output
    BlockCopy(output, input);
    state = ( state_t * )output;

    Key = key;
    KeyExpansion();

    // The next function call encrypts the PlainText with the Key using AES algorithm.
    Cipher();
}

void AES128_ECB_decrypt(uint8_t *input, const uint8_t *key, uint8_t *output)
{
    // Copy input to output, and work in-memory on output
    BlockCopy(output, input);
    state = ( state_t * )output;

    // The KeyExpansion routine must be called before encryption.
    Key = key;
    KeyExpansion();

    InvCipher();
}

#endif  // #if defined(ECB) && ECB

#if defined(CBC) && CBC

static void XorWithIv(uint8_t *buf)
{
    uint8_t i;
    for (i = 0; i < KEYLEN; ++i)
    {
        buf[i] ^= Iv[i];
    }
}

void AES128_CBC_encrypt_buffer(uint8_t *output, uint8_t *input, uint32_t length, const uint8_t *key, const uint8_t *iv)
{
    uintptr_t i;
    uint8_t   remainders = length % KEYLEN; /* Remaining bytes in the last non-full block */

    BlockCopy(output, input);
    state = ( state_t * )output;

    // Skip the key expansion if key is passed as 0
    if (0 != key)
    {
        Key = key;
        KeyExpansion();
    }

    if (iv != 0)
    {
        Iv = ( uint8_t * )iv;
    }

    for (i = 0; i < length; i += KEYLEN)
    {
        XorWithIv(input);
        BlockCopy(output, input);
        state = ( state_t * )output;
        Cipher();
        Iv = output;
        input += KEYLEN;
        output += KEYLEN;
    }

    if (remainders)
    {
        BlockCopy(output, input);
        memset(output + remainders, 0, KEYLEN - remainders); /* add 0-padding */
        state = ( state_t * )output;
        Cipher();
    }
}

void AES128_CBC_decrypt_buffer(uint8_t *output, uint8_t *input, uint32_t length, const uint8_t *key, const uint8_t *iv)
{
    uintptr_t i;
    uint8_t   remainders = length % KEYLEN; /* Remaining bytes in the last non-full block */

    BlockCopy(output, input);
    state = ( state_t * )output;

    // Skip the key expansion if key is passed as 0
    if (0 != key)
    {
        Key = key;
        KeyExpansion();
    }

    // If iv is passed as 0, we continue to encrypt without re-setting the Iv
    if (iv != 0)
    {
        Iv = ( uint8_t * )iv;
    }

    for (i = 0; i < length; i += KEYLEN)
    {
        BlockCopy(output, input);
        state = ( state_t * )output;
        InvCipher();
        XorWithIv(output);
        Iv = input;
        input += KEYLEN;
        output += KEYLEN;
    }

    if (remainders)
    {
        BlockCopy(output, input);
        memset(output + remainders, 0, KEYLEN - remainders); /* add 0-padding */
        state = ( state_t * )output;
        InvCipher();
    }
}

#endif  // #if defined(CBC) && CBC

#define AES_keyExpSize 176

struct AES_ctx {
    uint8_t RoundKey[AES_keyExpSize];
    uint8_t Iv[KEYLEN];
};

// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static void AddRoundKey_ctr(uint8_t round, state_t *state, uint8_t *RoundKey)
{
    uint8_t i, j;
    for (i = 0; i < 4; ++i)
    {
        for (j = 0; j < 4; ++j)
        {
            (*state)[i][j] ^= RoundKey[(round * Nb * 4) + (i * Nb) + j];
        }
    }
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void SubBytes_ctr(state_t *state)
{
    uint8_t i, j;
    for (i = 0; i < 4; ++i)
    {
        for (j = 0; j < 4; ++j)
        {
            (*state)[j][i] = getSBoxValue((*state)[j][i]);
        }
    }
}

// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static void ShiftRows_ctr(state_t *state)
{
    uint8_t temp;

    // Rotate first row 1 columns to left
    temp           = (*state)[0][1];
    (*state)[0][1] = (*state)[1][1];
    (*state)[1][1] = (*state)[2][1];
    (*state)[2][1] = (*state)[3][1];
    (*state)[3][1] = temp;

    // Rotate second row 2 columns to left
    temp           = (*state)[0][2];
    (*state)[0][2] = (*state)[2][2];
    (*state)[2][2] = temp;

    temp           = (*state)[1][2];
    (*state)[1][2] = (*state)[3][2];
    (*state)[3][2] = temp;

    // Rotate third row 3 columns to left
    temp           = (*state)[0][3];
    (*state)[0][3] = (*state)[3][3];
    (*state)[3][3] = (*state)[2][3];
    (*state)[2][3] = (*state)[1][3];
    (*state)[1][3] = temp;
}

static void MixColumns_ctr(state_t *state)
{
    uint8_t i;
    uint8_t Tmp, Tm, t;
    for (i = 0; i < 4; ++i)
    {
        t   = (*state)[i][0];
        Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3];
        Tm  = (*state)[i][0] ^ (*state)[i][1];
        Tm  = xtime(Tm);
        (*state)[i][0] ^= Tm ^ Tmp;
        Tm = (*state)[i][1] ^ (*state)[i][2];
        Tm = xtime(Tm);
        (*state)[i][1] ^= Tm ^ Tmp;
        Tm = (*state)[i][2] ^ (*state)[i][3];
        Tm = xtime(Tm);
        (*state)[i][2] ^= Tm ^ Tmp;
        Tm = (*state)[i][3] ^ t;
        Tm = xtime(Tm);
        (*state)[i][3] ^= Tm ^ Tmp;
    }
}

static void Cipher_ctr(state_t *state, uint8_t *RoundKey)
{
    uint8_t round = 0;

    // Add the First round key to the state before starting the rounds.
    AddRoundKey_ctr(0, state, RoundKey);

    // There will be Nr rounds.
    // The first Nr-1 rounds are identical.
    // These Nr-1 rounds are executed in the loop below.
    for (round = 1; round < Nr; ++round)
    {
        SubBytes_ctr(state);
        ShiftRows_ctr(state);
        MixColumns_ctr(state);
        AddRoundKey_ctr(round, state, RoundKey);
    }

    // The last round is given below.
    // The MixColumns function is not here in the last round.
    SubBytes_ctr(state);
    ShiftRows_ctr(state);
    AddRoundKey_ctr(Nr, state, RoundKey);
}

static void KeyExpansion_ctr(uint8_t *RoundKey, const uint8_t *Key)
{
    unsigned i, j, k;
    uint8_t  tempa[4];  // Used for the column/row operations

    // The first round key is the key itself.
    for (i = 0; i < Nk; ++i)
    {
        RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
        RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
        RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
        RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
    }

    // All other round keys are found from the previous round keys.
    for (i = Nk; i < Nb * (Nr + 1); ++i)
    {
        {
            k        = (i - 1) * 4;
            tempa[0] = RoundKey[k + 0];
            tempa[1] = RoundKey[k + 1];
            tempa[2] = RoundKey[k + 2];
            tempa[3] = RoundKey[k + 3];
        }

        if (i % Nk == 0)
        {
            // This function shifts the 4 bytes in a word to the left once.
            // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

            // Function RotWord()
            {
                k        = tempa[0];
                tempa[0] = tempa[1];
                tempa[1] = tempa[2];
                tempa[2] = tempa[3];
                tempa[3] = k;
            }

            // SubWord() is a function that takes a four-byte input word and
            // applies the S-box to each of the four bytes to produce an output word.

            // Function Subword()
            {
                tempa[0] = getSBoxValue(tempa[0]);
                tempa[1] = getSBoxValue(tempa[1]);
                tempa[2] = getSBoxValue(tempa[2]);
                tempa[3] = getSBoxValue(tempa[3]);
            }

            tempa[0] = tempa[0] ^ Rcon[i / Nk];
        }
#if defined(AES256) && (AES256 == 1)
        if (i % Nk == 4)
        {
            // Function Subword()
            {
                tempa[0] = getSBoxValue(tempa[0]);
                tempa[1] = getSBoxValue(tempa[1]);
                tempa[2] = getSBoxValue(tempa[2]);
                tempa[3] = getSBoxValue(tempa[3]);
            }
        }
#endif
        j               = i * 4;
        k               = (i - Nk) * 4;
        RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
        RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
        RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
        RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
    }
}

static void AES_init_ctx_iv(struct AES_ctx *ctx, const uint8_t *key, const uint8_t *iv)
{
    KeyExpansion_ctr(ctx->RoundKey, key);
    memcpy(ctx->Iv, iv, KEYLEN);
}

void AES128_CTR_encrypt_buffer(uint8_t *input, uint32_t length, const uint8_t *key, uint8_t *iv, uint8_t *output)
{
    uint8_t         buffer[KEYLEN];
    struct AES_ctx  ctx_instance;
    struct AES_ctx *ctx = &ctx_instance;
    AES_init_ctx_iv(ctx, ( const uint8_t * )key, ( const uint8_t * )iv);

    unsigned i;
    int      bi;
    for (i = 0, bi = KEYLEN; i < length; ++i, ++bi)
    {
        if (bi == KEYLEN) /* we need to regen xor compliment in buffer */
        {

            memcpy(buffer, ctx->Iv, KEYLEN);
            Cipher_ctr(( state_t * )buffer, ctx->RoundKey);

            /* Increment Iv and handle overflow */
            for (bi = (KEYLEN - 1); bi >= 0; --bi)
            {
                /* inc will overflow */
                if (ctx->Iv[bi] == 255)
                {
                    ctx->Iv[bi] = 0;
                    continue;
                }
                ctx->Iv[bi] += 1;
                break;
            }
            bi = 0;
        }

        output[i] = (input[i] ^ buffer[bi]);
    }
}